NICE, France — The Bastille Day fireworks had just ended above the waters of the Mediterranean and the broad Promenade des Anglais of Nice was full of thousands of spectators, many of them children allowed to stay up for the annual celebration, when the killing began.

The instrument of terror was an ordinary white truck. Its driver plowed through traffic barriers, then zigzagged through the crowd on the broad walkway while reportedly firing a weapon out the window. Scores of people lost their lives, scores more were injured.

A local lawmaker, who was in the crowd to see the fireworks display, said it was a female police officer who eventually ended the murderous rampage.

“A person jumped onto the truck to try to stop it,” Eric Ciotti told Europe 1 radio. “It’s at that moment that the police were able to neutralize this terrorist. I won’t forget the look of this policewoman who intercepted the killer.”

By then, the the crushed bodies of men, women, and children lay sprawled on the promenade.

In the aftermath of the horrific attack, officers found an identity card in the truck belonging to a Nice resident who was born in Tunisia.

The suspected attacker was named in the local press as Mohamed Lahouaiej Bouhlel, a delivery driver who lived in the city’s northern suburbs. French media reports suggested the 31-year-old man had a violent criminal record.

Tunisian security officials told Reuters that Bouhlel was born in Msaken, the hometown of Tunisian President Habib Essid. He was married and had three children.

Neighbors told BFM TV that he was a rude loner who was "more into women than religion."

The Promenade des Anglais was completely blocked off the morning after the massacre, the truck was still there and you could see the windshield riddled with bullet holes.

The signs of violence otherwise were few; apart from bits and pieces of discarded clothing. A woman’s high-heel shoe lay in the gutter. The beach was completely empty except for chairs and umbrellas that were going unused; the sea was sparkling blue under a bright sun.

At one end of the promenade, the world has descended with dozens of camera trucks and correspondents arraying themselves in front of the empty road.

Just a few hours earlier, Terri Clarke, a 49-year-old Scottish woman who has lived in Nice for 12 years, was watching the fireworks. She and a friend had been sitting on a green strip in front of the Hotel Negresco when all hell broke loose.

“Everyone got up to leave the beach and the road, and that’s when the bastards did this,” she told The Daily Beast of Thursday’s truck attack, which French authorities said left at least 84 people dead. President Hollande said 50 people were still in a critical condition "between life and death"—more than 50 injured children were taken to hospitals overnight. The attack is the deadliest in France since the Nov. 13 Paris attacks, which killed 130 people.

French Prime Minister Manuel Valls described the massacre as a “cowardly terrorist attack.” No link to the so-called Islamic State has been established but various jihadi groups have long had a foothold in some of the neighborhoods on the fringes of the famous port and resort town.

“At first I thought it was part of the show,” Clarke said. “Then I heard people screaming.” A spokesperson for the interor ministry said the driver opened fire and was shot dead by police. It is unknown if the driver acted alone.

“The [truck] was zigagging over to the bike path and back on the road, trying to kill as many people as possible,” Clarke said. “The only reason we’re alive is that we were in the middle of the street. I’ve never seen anything like this in my life. I’ll never get over it.

“The [truck] was going really fast by us, and after it passed I saw all these bodies lying in front of us on the opposite side of the street,” Clarke said.

“The bodies didn’t look real. They didn’t even look like real people. They weren’t moving and they looked dead. Nobody stopped to help them because someone was yelling about bombs and it was total chaos. I barely made it home because the crowds were so wild and terrified you couldn’t make any headway.”

Clarke said she could not understand how the van got on the seaside Promenade des Anglais. “The place was roped off. Where did it come from?”

Christian Estrosi, the president of the region, said the truck was loaded with arms and grenades, the Associated Press reported.

Veronika Prokudina, a 24-year-old Russian national, was celebrating a friend’s birthday at the chic Beau Rivage Hotel on the Promenade just after the fireworks display ended on the beach. She told The Daily Beast she and her friends “suddenly heard the sounds of people screaming and a big crash. We didn’t have any idea what it could be. It was like nothing I’ve ever heard before.”

Prokudina said she and her friends started to leave the restaurant, but as they did two policemen came up and ordered them and the other customers down into an underground floor at the Beau Rivage.

“Everyone was panicking,” Prokudina said. “We heard reports that shots were going off [nearby] at the Place Massena and on the Cours Saleya. My father had left early and I was so worried about him, but he just texted me that he’s safe. It’s madness and so scary.”

Philippe Lescos said he was a block away from the beach area where the attack took place and joined the crowds that he said materialized rapidly. He said he ran home to his apartment on the Rue de France.

“People were running like crazy people in all directions. The kids were crying and a lot of the adults were crying as well,” Lescos said. “We’ve been told to stay in our homes and not go out.”

A U.S. official reached by The Daily Beast said American authorities had no means to confirm that ISIS was responsible, but were already listing it as a top suspect. Initial reports suggested that Telegram messaging app accounts affiliated with ISIS were posting photos from the attack. But since the accounts were not confirmed and there was no official confirmation from ISIS, it was impossible to say authoritatively the attack was the work of the terror group.

“I condemn in the strongest terms what appears to be a horrific terrorist attack in Nice,” said President Obama. “On this Bastille Day, we are reminded of the extraordinary resilience and democratic values that have made France an inspiration to the entire world, and we know that the character of the French Republic will endure long after this devastating and tragic loss of life.”

Mohamed Benzimra, who lives in one of the heavily Muslim neighborhoods that abut Nice, is a local Muslim activist who has long preached against ISIS. “We don’t know for sure, but this has all the earmarks of ISIS,” he said. “If it’s them, it’s no surprise. The only surprise is that Nice wasn’t hit earlier.”

Bastille Day, or la fête nationale, is celebrated every July 14 in France. It marks the storming of the Bastille prison during the French Revolution in 1789.

Nice celebrates Bastille Day with a fireworks display on the beach every year. It is one of the most heavily attended events of the summer season which is in full swing. The Promenade des Anglais, where the truck ran over the victims, is one of the most popular seafronts in Europe.

A longtime resident of Nice named Andy Dwyer said he was walking his dog along the Promenade right after the fireworks display ended.

“All of a sudden I heard screaming and I saw crowds running toward me,” Dwyer said. “Everyone was ducking and diving to get away from the [truck].

“The Promenade was packed. Literally thousands of people lined up four and five deep were standing there watching the fireworks. They were like sitting ducks.

“People were lying dead on the street,” Dwyer continued. “One was just a child... I saw a man with his legs cut off. I think he was already dead. The terrible part was that I wanted to help but I didn’t know what to do. Bodies were everywhere. People were roaming around them, running, screaming, and crying.”

“I was terrified,” Clarke, the Scottish expat, said of witnessing Thursday’s attack. “The weirdest thing was that the minute the police stopped the [truck] these gale force winds come up and there was a huge sudden storm. The terror on the faces of the children was terrible.”

—Reporting by Christopher Dickey in Paris and Dana Kennedy in New York. Additional reporting by Nancy A. Youssef, Andrew Kirell, and Gideon Resnick.